Some experiments are already taking place in the mine at a depth of about one thousand five hundred meters.

VOA: special.2009.07.21

Mario Torres Lopez, 42, was working at a depth of about 100m (328ft) when the mine collapsed.

BBC: Chile slow search for miner trapped 100m underground

Valarmadhy inches forward, using small tools to clear a strip 1m (40in) wide, digging down to 6in - the accepted safety depth - to ensure there are no mines between herself and the nearest visible mine.

BBC: The women clearing Sri Lanka's mines

The San Jose mine collapsed on 5 August 2010, cutting off the miners at a depth of more than 700m (2, 300ft).

BBC: Chile marks year since mine collapse